The proposed studies are designed to elucidate surface modifications of ram spermatozoa during incubation in vitro (or in vivo) in female reproductive tract secretions. These secretions are collected continuously from conscious ewes through catheters inserted surgically into the Fallopian tubes and uterus. Glycoproteins of sperm cell surfaces and fluids will be selectively labeled in their tyrosine residues, and galactose or sialic acid termini. Total dodecyl sulfate-soluble proteins will be fractionated by one- one and two-dimentional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Labeled surface components will be distinguished from unlabeled proteins by autoradiography of the dried gel slice. We will identify labeled surface proteins removed from spermatozoa during incubation in uterine and oviduct fluids and study labeled fluid components adsorbed by spermatozoa. Furthermore, the surface protein pattern of capacitated spermatozoa will be characterized and the potency of female reproductive tract secretions determined in relation to the estrous cycle. Then we will study surface renovations of capacitated spermatozoa in cauda epididymal fluid (CEF). Labeled CEF components adsorbed by capacitated spermatozoa will be identified. Finally, attempts will be made to relate the anticipated surface changes during capacitation and decapacitation to energy metabolism and motility of the spermatozoa. Criteria for energy metabolism will be: concentration of ATP, cyclic AMP, respiration and glucose utilization. The proposed studies will focus particularly on specific surface and fluid proteins that may play a role in the energy metabolism and motility of spermatozoa in the female reproductive track. The project should increase our understanding of surface modifications that occur in spermatozoa before fertilization.